Caleena and Rejina

Twin maids serving the Princesses of Gold and Silver at Iselma.
Obviously, for the “production” of the Princesses, the ones who took care of them would also need a similar Concept. For that reason, Iselma set up a system to produce a large number of twins among their branch families.
Because of this underlying system, Aozaki Touko was able to turn Caleena into the Princess of Gold with her plastic surgery.
Furthermore, as mentioned in the story, there is actually a third sister still living in their hometown. Even if she didn’t know about the sad fate of her older sisters, El-Melloi II sent her a letter that she might at least find some happiness.

Lord El-Melloi II Case Files material: Lord El-Melloi II Case Files Glossary